How Do Drive and Serpentine Belts Work?

The drive belt on your vehicle delivers power to the car’s engine, alternator, water pump, power steering pump, and air conditioner compressor. Usually, a car has one or two drive belts, and if there is only one, it is often referred to as a serpentine belt.

The drive belt is constructed from sturdy rubber, but eventually, it will sustain some wear. You can usually expect it to last up to 75,000 miles, but most mechanics recommend replacing it at the 45,000 mile mark, because if it breaks, you won’t be able to drive your car. And if the engine runs without a belt, your coolant won’t circulate, and your engine could overheat.

How do you know if the belt needs to be replaced?

You’ll probably notice chirping or squeaking sounds. If you do, you have your mechanic examine the belt. Splits, cracks, missing chunks, damaged edges, and glazing are all indications of excessive drive belt wear, and the belt should be replaced. You should also have the drive or serpentine belt replaced if it has become soaked in oil – it might not cause a problem right away, but oil is one of the leading causes of drive belt damage so immediate replacement is advised.

Loose belts are also a problem. Most cars today are equipped with a belt tensioner that works automatically to ensure that the belt is always properly adjusted, but some still require manual adjustment. A rattling sound can be an indication that your drive belt tensioner is faulty.

What causes drive belt wear?

One of the most common causes of excessive and premature belt wear is a misaligned alternator. When the alternator is misaligned, so is the pulley that moves the belt. Another cause is a missing or damaged engine under shield, this is what protects the belt from water, dirt, small rocks, and other compounds that can cause it to wear more quickly. Oil or coolant leaks and improper tension can also cause wear.

Don’t take chances

Don’t neglect your drive belt. The last thing you want is to end up roadside with an overheated, badly damaged engine because your water pump or cooling system failed, or to lose your power steering on a tight curve. Don’t risk damage to your car’s engine, or to yourself.


The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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